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Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of next week, and while we can hopecast for a front/kink/trough to appear in exactly the right place for every IMBY desire it is frankly impossible at 7 days' range. We wouldnt even try to get that right on a standard westerly atlantic pattern - how can we hope to get close to specifics 5 - 10 days out from the main event when we are seeing dramatic events unfold in the strat? Remember - we are still in reversal for several days yet, and the models will have larger than usual error bars on microscale events.
We couldnt hope for a better anomaly chart to see in the new month
and this is a belter from GEFS to kick off the week on Monday
And the strat? By day 10 it has reformed over the pole as the reversal ends, but the shattered remains at 10hpa are weak, and a large eurasian block is still in place
while zonal wind profiles recover to weak levels over the pole, but see a very muddled profile at 55/65N suggesting anything but a recovery. Sustained chance for high lat blocks to survive in situ though the storm track will gently slide back north. Battleground snow?
Down at 150hpa blocking clearly still in place over Greenland
So - 10 days of almost zero chance of a substantial change to the pattern, and decent confidence in any recovery from this point being slow and painful for the vortex. Next week will be very cold as we know...and the week after will also be cold, quite possibly for all parts throughout the week. Confidence then less sure by week 3 - need to see how pacific forcing may impact at that point, and just how quickly (if at all) the vortex recovers. If it is too late for a recovery then kiss goodbye any early spring as cold will continue to spill out at times right through the month in all probability.
And what about snow next week? Well - I think all this hand wringing over each individual model is a waste of energy.... but maybe history can help. 3 days before we were hit by substantial snow in 1991 the charts looked like this
3 days before the snow hit in 1987
We are forecast currently to look like this in 72 hours BUT we know we have an SSW in the bag and a signal for sustained blocking and a retrograde pattern
Which would you rather have?? Both 1991 and 1987 delivered plenty of snow. What do you think is likely from here if they are analogues to go by in terms of snow fall... - and what about the signals for longevity listed at the top of this rather long post?? The only thing going against us this time is the calendar date.
All very very good. People criticising this setup really and truly need to get their history goggles on and then wander off to a quiet corner, tail between legs.

I think too many have already become desensitised to what constitutes a 'fantastic chart' and the seasonal ailment of this thread (which is irrationally mood driven anyway by the more average synoptic charts that are customarily on offer) has taken on a latest variant of becoming superimposed and twisted on the absurd semantic that 'merely' only UK Tundra conditions are being shown and not the Canadian variety.
Truly, if you cannot exercise self control in front of your lap-top by the smorgasbord of dessicating cold solutions evident on NWP, especially as we are heading right into meteorological Spring, then its maybe best that a different form of self torture is considered to spare those who take a more considered perspective.
This has nothing to do with any regional bias (coming from a part of the country that relies on these increasingly rare sort of synoptic to get a snow fix) its to do with the usual fascination I have for sitting back and marvelling at watching a pattern like this unfold in the greater macro scale.
If/when it snows at home, I will be less inclined to spend spare time waiting for when it is next going to snow, or when its going to end - but instead getting out, having fresh air, exercise and enjoying it.
And then, when the snow and ice is over, it will be a case of seeing how the patterns evolve through Spring and into Summer - looking for the best that can be on offer for this Island, whose micro climate is fickle, elusive and overly too mobile to the sort of sustained blocked patterns that can be the deeply cold derivative as upcoming next week, or depictive of deep Azure blue skies, sunshine and warmth of the summer.
Get used to this reality - it will always be thus

Another great day of model output with no concerns from me with what is shown.
2 points
First is that the worst model output that we have seen today and the last few days is far better than the best output that we have seen for many a year. So don't be concerned with operational variations.
The second is that normally any shortwaves scuppers any cold spell, but in this case I welcome shortwaves because once that cold air is embedded ( and movement will always be west of the general pattern), then we have shortwave snow making machines on our hands. The more shortwaves the better as far as I am concerned because the large Greenland block will keep us embedded in deep cold....
Just enjoy the output and whatever it brings.

I quite often agree with your sort of sentiment, as I'm one who opts to look at the most likely solution to fit the signals rather than the preferred one
But, equally impartially and with intended objectivity (hopefully):
The situation at present is a highly unusual one and the risk of some astonishing late season wintry weather is much higher than usual, certainly than often seen in these cases where deep cold pool advection flirting with the UK graces the perimeters of more 'reliable' NWP
The repercussions of this SSW are going to be sustained. The clock starting ticking back in January and carried on through this month with extreme instability of the atmospheric profile with the tropics and extra tropics being subjected to opposing high amplitude states of angular momentum tendency.
The impact on tropospheric global wind-flows (the Jetstream) has been significant, in addition to the detonation of some intense cold pooling over the polar field (relative to the modern day generally warmer arctic) : more especially across the Canadian arctic as multiple programmes of hot needles are probed into the polar stratosphere
The result of extreme tropical momentum and stratospheric implosion implies high impact weather events on a broad-scale. Some places are going to get bitterly cold and some weirdly warm.
In this day and age fewer parts of a hemisphere can get cold with less to go around than used to be the case maybe. But this programme of events strongly favours the European sector to become bitterly cold from what looks to be an impressively large breakaway cold pool for the time of year from Siberia. While its true that the envelope of this cold has boundaries that shift in intra suite modelling, the focus of the BI being impacted in inclusion, is much higher than other situations where lesser broad-scale drivers have been in evidence
Ramping indeed requires a justification - I think this situation fits that criteria. Areas of land mass infrastructure most at risk aside from weather impacts (hopefully with least human welfare risk), the synoptic blocking pattern and its associated reverse polarity from one side of the Northern Hemisphere to the other - is not something seen on an every day NWP menu

Dear wife,
Due to the netweather code of conduct I am unable to tell you this directly now as, otherwise, this will go pear shaped and as we haven’t seen lying snow for 5 years... I can’t risk that.
If today’s icon/gfs 00z (17/02/18) charts verified, we could be in for the snowiest spells of weather we have seen in our 40 years living in the south and this could pretty much be a nationwide event. I know that you hate and loathe cold, snowy weather but all I can say is........ get to Tesco’s and stock up on supplies, alcohol and logs as we’re in for the long haul!!!
All things going well, I will show you this message on Tuesday/Wednesday as I may be allowed then!!!
Amazing charts today, not sure the ecm 12z from yesterday could be beaten but it may have been by icon/gfs 00z runs. Great to see the ukmo onboard, need the ecm back on board later today.
Enjoy the ride!
Clem (suffering in silence!)

Sorry, I just thought I’d walked into the moans threa.. oh wait. <passes around a big bag of grips> No sooner do we get a cold spell within sight it astonishes me that time and time again some people seem hell bent on being the first to find signs of it unravelling. Is there some kind of prize for this I don’t know about? We don’t live in Siberia. We are never going to have three month of bitter cold. We all know this!
It’s one run. 48 hours ago some of you were dismissing the idea of an easterly entirely based on the output.
Maybe when the hangovers and cruddy moods have lifted this will improve the quality of posts?

Well it's a wonderful sunny day down here in Exmouth and 12c right now and set to continue (here) for 4-5 days with overnight frosts but gradually cooling off by day. The south-east will be the first to see the cold weather biting and some early snow flurries (perhaps by the weekend?). Very few people will believe us or the MetO etc (and certainly not the Daily Express - crying wolf far too often) that we are heading into deep cold!
This benign, sunny and mild weather reminds me of what proceeded many of our severe cold spells and I thought that it would be the perfect time to compare some of these to the current and predicted patterns. Before my time, it was very mild in mid-January going into the 1947 epic cold spell. At age 3 (before I can remember), it was very mild prior to the severe cold of early Feb '56. Then my actual experiences started with the '62/'63 winter. Some early cold and snow in November and early December. Then cold and foggy. Then mild and benign for a week and then from Dec 25th, sudden cold and snow and 11 weeks of winter wonderland. There are other and more recent examples, including February 1991 and March 2013 which some have already alluded to. What many of them have in common is the HP building into the country (either Azores HP ridging north-east, HP developing right over us or HP ridging down from the Arctic or Scandi). They all brought in winds from a southerly quarter with mild and benign conditions. Then the Siberian or Arctic (or in between) HP built and the wind backed into an easterly or north-easterly quarter. It actually all makes sense. Almost all of these spells started slowly and then the doors to the freezer were suddenly flung open.
BEFORE AFTER
1947
1956
1962
1991
2013
2018
I believe that we'll be referring back to the 2018 severe cold spell as an analogue for many years to come.
I'll be back with one of my Eurasia temperature and snow cover reports towards the end of this week. Everyone enjoy watching this all unfold. It's going to be something highly memorable.

So, that's another couple of people blocked from posting in here, any more takers?
Those wanting to just moan for moanings sake, please head to the moans thread. Those wanting to troll, please do one. Those wanting to discuss the models, please carry on

Posted February 10
Irrespective of what the ECM goes on to show shortly and irrespective of what my head keeps telling me of how the effects of this SSW could be mitigated, I am not sure I have seen anything programmed quite like this thing.
Polar easterly reversals are often enough mitigated at least to some degree by other tropospheric drivers, but I am beginning to come to round to thinking this may not be one of them where that happens so easily and its going to take over a lot of the NH for some time.
it could be the case that it would start to be more prudent not to underplay the SSW, than place caveats as to what might mitigate it. On that basis maybe its me who should have a bit of a ramp, and not others who should restrain themselves
However it plays out in terms of what comes out of the sky in the coming weeks - and despite the fact that the actual phenomena of SSW's is not new, this is quite a significant specimen indeed we are watching unfold
............................................................................
A week on, and a crazy amount of pages later, what has changed?
Well I haven't had another ramp, and the deepest cold is still 9/10 days away
But what has become clear in the course of a week is that the first stratospheric break-down salvo is set to verify for certain this week - and that day 9/10 day period marks Phase 2 and the time when the Canadian vortex to the NW should finally back off and the down-welling process of -ve zonal wind anomalies really start to make themselves felt in out part of the Northern Hemisphere
On that basis we can give credence to the shape of the mid and higher latitude pattern and emerging block alignment with the deep cold backed up like a dam waiting to be unleashed
I am amongst the most sceptical of day 10 UK deep cold in NWP and very often based on the realistic signals, barely take a second glance, if even much of a first glance at all
But this SSW is a significant specimen indeed, and no further deep analysis is needed. On that basis I will be taking this particular day 10 deeper cold rathe more seriously as a contender
The fact that Phase 2 marks the time when the strongest sibling vortex lobe starts to finally cave in after its winter rule, increases the chances of deeper cold air advection at that time-period not just because the block to the NE can start to orientate in ideal position as polar jet energy is finally being squeezed out, but because the chances of retrogression are also much higher so that at some stage re-loading deep cold has a heightened chance of finding out even this little Island.
Probably the most simplified basic principle post you will get from me - but less is more sometimes and nothing else needs to be added

Also..
Please remember that there are loads of unseasoned folks reading the thread so whilst your tongue in cheek comment might register with frequent visitors, it may well be completely baffling to most. It’s easy to think that the board is just the same 10-15 people reading and posting but there are 500+ on tonight. Don’t be a dick in front of 500 people, I guess is my message.

Looking, or rather skimming through the last x pages from late afternoon, reiterates why I do not spend too much time in here.
Some of you for goodness sake have a walk outside, watch the tellie, talk to a real person away from the pc. What you are watching is the weather models trying and slowly but surely, as they always do, come to a concensus about what is happening. Quite why folk worry about T+240 and beyond when most predictions by the models at that range are highly prone to change is beyond me. Deep cold is 85-90% likely to occur, it has never really been sensibly predicted by any of the more serious posters assessing the various outputs to occur before 23-25 February. That was two weeks out. Now within a week of the second date that is being refined to more like 25-26, so what? Get a grip and become realistic, they are models created by humans, are you perfect?
end of jh rant.
here is the latest link to NOAA 500 mb anomaly charts. This level, approximately 18,000 ft is far easier to predict than the surface, these are mean charts, but they are about 70-75% close to what occurs in about 80% of cases. Yes they are wrong at times but not often.
http://www.cpc.noaa.gov/products/predictions/610day/500mb.php
To me, using them every day for about 7 years and during the winter for 10 years or so I cannot recall seeing charts showing any more solid northern blocking for the time scale they are showing, this for at least 3-4 days. That includes the deep cold much of the country had in late Novemeber-December 2010.

Hello to the Net Wx comic, I suppose it's not tea you are drinking A
Good to see you on form and markedly misunderstanding the models as usual
take care young fella
oh just to confirm that the flow is going to come from east not west from later this week and into March, below the links to the latest NOAA 500 mb anomaly charts. They have been consistent for several days now with what they show this evening. Just how cold and how much snow not even Anyweather has any real idea. The synoptic models will to and fro about this over then next 4-5 days. So really interesting model watching.
http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

The high goes further north and the moaning starts , it goes south and the moaning starts !
Seriously what’s going on?
The GFS didn’t follow the ECM which is great news.
I think I might come back when some sanity returns to this thread!

I don't think there are any words that can describe these synoptics, lol. All my SSW dreams coming true - this is the perfect SSW trop response that excited me so much 2 weeks ago. Can't believe that it can come true - Can it?

I think BA is simply reinforcing the point that it’s not really worth attaching too much credence to current output, where there is clear inconsistencies being exhibited. It really is more about broader trend and the eventual path, whereas the journey to get there remains fluid and undecided. 12z EC could correspond with its peers or it could reinforce its 0z signal and advertise a more subtle path.
What I would strongly disagree with, is NWP assertion of a quick return to mobility (or milder weather) That evolution doesn't correspond to mid range products at all, and can quite confidently be discounted as models reverting to type and to some extent underestimating the degree of in situ blocking. This behaviour has been seen previously so reasonable to view a rapid breakdown with scepticism.
What an exciting end to winter!
SB

It baffles me how some are managing to find negatives in the current output. It is not being delayed, no idea where you're getting that from. If you can't enjoy the current output then you'll never enjoy any winter synoptic set up.

If anyone has the patience to look through the ECM ensembles on weather.us, make sure you do tonight, go to Thursday March 1st, look at 850hpa / temperature and scroll through all 51 members. You may never see anything like it again.
The number of runs bringing minus 16C uppers into the E of England is staggering, truly staggering. Probably 50% of the runs or more on either the 1st or the 2nd - it's the majority!
It's only a few nutcase runs that is keeping the mean nearer minus 10C.
A lot of runs get to minus 17C, and two runs even get the minus 19C line to the east coast.
The number of UK wide ice days is also quite incredible, and you'd have to think the UK minimum daytime record for March (-4.6C according to the Met Office) would be under major threat somewhere.

Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Get the cold in then the snow comes ...
Everyone got the message yet????!?? There is NO POINT in looking at anything after the 3-5 day mark. It WILL change.
* Do we have cold coming?? YES
* Will any precipitation fall as snow and not be marginal???? YES
...Then yes we are sorted people!!!! Come back and look at precipiation from Monday morning onwards ...

I've had a great idea, we could make some other threads and areas on the forum for people to discuss all sorts of other topics that are accessible with just a couple of clicks, then this thread can be kept to just model discussion? Oh wait....

I'm here - been working and have also had to pick myself off the floor after checking the 12Z.
Best ever trop response that we have been able to track following a SSW, oh those of little faith lol.
I did think of buying all the snow shovels and salt in B&Q yesterday and then selling it back to them next weekend....
I have been convinced of an epic cold spell for a long time now (since before the split but my resolute belief was reinforced when I saw the residual Hudson Bay daughter vortex getting taken down).
It may have taken the best part of 10 years but finally we are seeing the makings of an epic spell when you take the strat vortex out of the equation. Even @TEITS may finally have to concede that there is something in this teleconnections Malarkey!

Afternoon, as promised reporting back with our Forecasting Portal Service experts latest thinking with specific the United Kingdom regarding depth of cold , timing and snowfall. They talk about the large cold block in place over much of Europe by Wednesday with Britain well locked in its midst based on the model 300mb wind flow pattern over much of the Northern Hemisphere which looks conclusive to a prolonged cold spell. Their own model develops a core mass of very cold upper air now developing over Northern Russia, sub -40c core at 500mb level ( at around 18500ft asl). They predict this cold pool to move W/SW in the direction of the British Isles with a quicker solution than shown by some of the bigger models. Further into the middle of next week looks like a trough or low formation to develop in the flow ,possibly over Poland or Southern Baltic as they have pressure value falling as low as 1015mb. That's something to keep an eye on in later runs. So light snow could start showing up in Southeast parts later in the weekend but the heavier convection snow more likely in Eastern parts in earlier part of next week with possible chance of more organised snowfall by Wednesday or the first day of the new month. So all in all follows UKMO latest forecast regarding snow prospects but the difference could be timing. Hope this all helps.
C

All this fuss about downgrades - 'chill' out !
Looking at two runs 24 hrs apart so examine the same time stamp - from last night's 12z to tonight with a helpful Polar Bear diagram included.
As you can see the Polar Bear still on course to arrive, just a slightly less ferocious looking bear this evening..

WHY I BELIEVE THAT THE GFS OUTPUT FOR WEEK 2 WAS COMPLETELY WRONG
My post yesterday (now buried on page 2 of this thread) compared the run into to the predicted upcoming cold spell to some earlier severe spells dating back to 1947 and up to 2013. I will make further reference to the March 2013 spell towards the end of this post when I compare it to the current and predicted set up. I intend to demonstrate with plenty of evidence why I feel that the GFS is being far too progressive in bringing back the Atlantic after the turn of the month. In fact, I do not necessarily see this happening until well after mid-March, although one or two very brief less cold interludes can never be completely ruled out. This was based on the previous few runs up to today's 12z. I see that the 18z (which rolled out while I was writing up this post) has a slightly colder solution again but still ends with less cold uppers over the UK and is a long way from the 12z ECM and UKMO solutions..
CURRENT PATTERN AND CONDITIONS
In summary, the record strength sudden stratospheric warming (SSW) has fully impacted and reversed the winds with the Arctic cold being displaced towards the middle latitudes. The jet stream has weakened and split and the Atlantic LP train has ground to a halt. The persistent and very strong Canadian PV is coming under attack and all models show it breaking up over the next few days with the main lobe transferring across the Arctic to Siberia during the next week of so. The blocking patterns are becoming established. During the next few days, the HP close to the UK is set to link up with a vast expanse of HP extending from northern Siberia through Russia and pushing westwards to Scandinavia and beyond. Once established, this is likely to dominate the pattern for many days if not weeks. The deep cold over north Asian and Siberia is surging westwards. I show the "current" charts below from the 12z run. I used the GEFS simply because it starts with T+0 (GFS operational run starts with T+6):
Jet Stream Surface Pressure 850 Temps 2m Surface Temps
Now, I'll go through this in a little more detail. I had a glance through the strat thread to get the latest on the SSW and I must thank @Blessed Weather for directing me to @chionomaniac's analysis of the significant second warming which has effectively to quote "knocked out the sister vortex over the Hudson Bay and will cause the NAO to go strongly negative". In simple terms this means that the Canadian lobe of the vortex will be more or less destroyed (as will be seen in the later charts below) and the remaining fragments are being pushed away across the Arctic. I have also seen the comments from a number of the strat specialists that the record strength SSW and the further warming will extend into the "final warming" which normally occurs as we move into Spring (in March/April but can be a few weeks earlier or later). This means that the PV will not reform until towards next winter. Assuming that this is correct (and I have absolutely no reason to doubt it) then the wind reversal will continue for an extended period and HLB patterns will be maintained for many weeks as reflected in a strongly negative AO (Arctic Oscillation) from later this week and the Atlantic will be blocked with LPs making little of no progress against the HP block and being forced much further south as reflected in the NAO (North Atlantic Oscillation) about to go strongly negative too.
The current pressure chart shows that strong Canadian lobe right now. The jet stream is already starting to buckle, looping around the north of the building Atlantic HP. The stronger streak pushing out of North America is already bending southeastwards. There is a fairly strong southern arm pushing though North Africa and well south of the Mediterranean. This is already a classic set up with the jet pushing LPs well to the south and on a nice clean and direct route. This should prevent any chance of an LP stalling and moving up through France and introducing winds from a more southerly quarter. Meanwhile the Atlantic HP is ridging strongly right up into the high Arctic. This in turn links up to the belt of HP already established over north-east Russia and Siberia. This pattern is now primed to evolve into a much greater area of HP which will become dominant and control the weather patterns in northern Asia, Russia, Europe, the UK and well beyond (as described in the next section). I included the temperature charts for general reference but I will not comment on them. I will be producing one of my Eurasian temperature and snow cover reports tomorrow with current sea surface temps and dew points too.
A WEEK FROM NOW:
Now let's have a look at what the 12z model output is telling us for the end of week 1. To keep this as brief as possible, I'll only compare GFS and ECM output. I know that there has been some very good output (for coldies) from the very consistent UKMO (but that only goes to day 6) and GEM falls into the same bracket. These are the 12z T+168 charts:
GFS: Jet Stream Surface Pressure 850 Temps 2m Surface Temps
ECM: Surface Pressure 850 Temps
Note how the jet stream profile has already changed completely. It has generally weakened and the northern arm is almost non existent. There is a small streak pushing south-westwards out of Scandinavian (part of the pattern reversal). All the energy is now in the southern arm which powers even further south through North Africa. There is a minor loop through France which is not entirely logical and may be part of the later GFS divergence later on (I'll return to this in a minute). GFS has completely smashed the Canadian PV lobe and it has been replaced by strong HP. The remains of the vortex are shifting across the North Pole on the way towards Siberia. The HP has built powerfully across form Siberia, through northern Scandinavia, onwards through Iceland and extending all the way into Greenland. The strong easterly has been established. Meanwhile, there is LP east of the Azores. There is also a small LP running south-westwards out of Scandinavia in the easterly flow (this type of minor feature as well as troughs and other disturbances cannot be accurately forecast a week in advance). It is dragging in some very low uppers and deeper surface cold behind it but this cold pool is moving our way anyway. Plenty of snow on that chart!
The ECM output for the same time is pretty similar but with subtle differences which will be important going forward. The Iceland part of the HP block is about 150 miles further south. The LP is in a similar position east of the Azores but there is a much cleaner and rather stronger easterly flow with no LPs embedded in the flow (at this stage). This stronger more direct flow is pushing the lower 850s right across the country. On this chart I would say that there may be snow showers in the south and south-east. With the flow marginally south of east, there could even be a rare Channel streamer which would produce a line of snow showers near the south coasts of Dorset, Devon and Cornwall. I moved down to Exmouth 3 years ago from Hertfordshire and other than seeing a few flakes on several occasions, we've been completely snowless.
INTO WEEK 2:
Here, Ill produce the same charts for day 10, the furthest out that ECM goes:
GFS: Jet Stream Surface Pressure 850 Temps 2m Surface Temps
ECM: Surface Pressure 850 Temps
The GFS shows a slightly changed jet stream profile. Most of the energy continues in the southern arm but there is a strange breakaway branch pushing into the UK. What on earth is the GFS reading here? They are trying to push the pattern northwards. They have mixed out the very cold uppers over western and central Europe and pushed the lowest values in northern Europe and Scandinavia. I have a theory for this. We know that the models find it difficult to cope with the impacts and pattern changes associated with an SSW and full wind reversal. GFS is trying to bring the Atlantic back in as if this was a temporary blocked pattern. This is definitely not the case. The Arctic pattern is still in full reverse flow mode and is unlikely to change back any time soon (perhaps not at all if the strat SSW and second warming merge into the final warming). This will maintain the blocked pattern. Yes the block will shift around slightly and the flow might back to northerly at times but the dominant pattern will continue to be from an easterly quarter. There is nothing to push the jet through the UK and the Atlantic will also remain relatively blocked. One cannot rule out a more south-easterly and less cold flow at times but the main cold block is much more likely to reload after each weakening, unless or until the Arctic reversal ceases. The SSW was so strong that it is likely to maintain powerful HLB for a prolonged period. .
The ECM solution makes so much more sense. They do slacken off the easterly but the direction of the main flow is still north-east to south-west. The LPs around the UK are all cold ones originating from the north-east. Yes, it's possible that one of them might bring in "temporarily" less cold air from the south, more especially down here in the south-west. The 850s are still -8s to -12s and that looks like a particularly snowy period if that chart verified.
DEEP FI - DAY 16:
Just a brief look at how the GFS continue with the 12z run.
GFS: Jet Stream Surface Pressure 850 Temps 2m Surface Temps
They have brought the Atlantic to life again with a moderate westerly flow and uppers going into positive territory. The jet stream hardly supports this pattern accept that there is a kink in the southerly track which brings a loop into the UK. It might even be that GFS shifts the pattern back southwards again later on but that doesn't explain their very progressive or completely wrong attempt to bring the Atlantic back to life. The last strong SSW impact was in March 2013. Quite a different build up with it being triggered in January and no two events will have exactly the same impacts and timings. The pattern went into full reversal back then too and that lasted for 6 weeks despite the deeper cold starting some two weeks later (around March 10th). let's now see how GFS handled that one with actual archived charts and GFS archived predictions:
GFS Archive Charts T+ 240 Forecasts, 10 days out:
For March 10th 2013 For March 10th 2013 For March 20th 2013 For March 20th 2013
For March 30th 2013 For March 30th 2013 For April 9th 2013 For April 9th 2013
NCEP Re-Analysis Actual Archived Charts:
Actual March 10th 2013 Actual March 10th 2013 Actual March 20th 2013 Actual March 20th 2013
Actual March 30th 2013 Actual March 30th 2013 Actual April 9th 2013 Actual April 9th 2013
Gosh, this was a trickier exercise than I imagined it would be. I'm afraid that you'll need to scroll back and forth to make the comparisons but I'll summarise the differences now. The GFS archive charts with their forecasts 10 days in advance are shown in the top two rows and then the actual charts for those same dates are shown in the bottom two rows. As you can see, there are considerable differences. The actual chart for March 10th 2013 has the easterly flow well established with -12c 850s flooding in. The forecast was for southerlies and +4c 850s. By March 20th the actual and forecast charts are a little closer with easterlies over the UK but the forecast had a stronger vortex remaining whereas the actual chart shows it broken up. The forecast had lower 850s for the UK than actually transpired. By March 30th GFS forecast had started to bring the Atlantic back in but that never happened - doesn'tthis problem seems very familiar! The forecast 850s were over +4c but the actual values were sub -8s! By April 9th, the forecast was for LP just starting to bring in milder south-westerlies but the actual charts shows east-south-easterlies! The forecast was for 0c to -2c 850s but the actual was -4c to -6c (a little closer).
Overall, this exercise was highly worthwhile. It shows that the GFS constantly wanted to warm things up and bring the Atlantic back in but that never materialsed during the entire 6 weeks. Despite their model being updated, I feel that they sinply have not learnt any lessons and still do not factor in flow reversals. Now with all this evidence I hope that many of those who are worried about the longevity of the cold spell being cut short should not look at the GFS in the extended period. So far, most of the other models seem to be doing a rather better job but in fairness to the GFS, the others do not go up to day 16. So, let's just use the day 10 charts as the evidence.
That's more than enough from me for now. I'll do one of my Eurasia temperature and snow cover profiles tomorrow (or Friday).
EDIT: I'm afraid that the white "run through" arrows for the charts are not appearing. Not enough editing time to change these now. I apologise for the inconvenience and will copy charts in a different way next time.

Just to give an idea of the temperature differences between the North Sea and cold uppers early next week, SSTs around 6-7C with 500mb temps between -40 to -45C next Tuesday as that upper trough moves over - giving 45-50C temp contrast and between sea level and 850mb it's a 20C contrast- certainly will create steep lapse rates and aid in cloud depth to produce some heavy snow showers over the N Sea.
Obviously the air will be dry when it leaves the near continent, but will pick up moisture in the lower layers over the North Sea which will rise into shower clouds given the low-level instability of cold air over the relatively warmer sea.

So to sum up in a detailed post developments in the UK for newer members before it picks up in here with the 12z's. Thought I would sum it up in a simple way. Imagine a conversation with someone from the UK and Eastern US about the current weather:
UK: I hope we have an unforgettable cold spell
Eastern US: Why is Europe turning so cold when we are so mild?
UK: Stratospheric Warming
Eastern US: Right... and you call it stratospheric warming despite the fact its going to be cold...
UK: Err yes
Eastern US: Good lord what's happening there!?
UK: Polar vortex lobe
Eastern US: A polar vortex lobe, at this time of the year? over Europe? Located directly within the United Kingdom?!!!
UK: Yes
Eastern US: May I see it?
UK: No
Eastern UK: Well this stratospheric warming strikes me as rather odd, but it does make for a good cold spell!
Looks like it's the Eastern US is going to be on the mild side this time! We'll let those in Albany enjoy their steamed hams...
Finally, thought I'd look back at some past events that didn't materialise but explain how this time things are different:
February 2012 January 2008 February 2001 December 1997
February 2012 - Very very close but high pressure ridged across us and the cold lobe of air was stuck over Denmark. This time we have an Azores low preventing that.
January 2008 - High is centered too far south to sustain westerly cold push. This time it's focused over Svalbard.
February 2001 - High too far north - A possibility but the ensembles aren't showing this now really.
December 1997 - The cold lobe of air coming from Siberia fails to move to Europe.
As I mentioned... I think this time is different. The only risk I can think of is if the Azores low becomes too influential and keeps the really cold stuff to our north. I reckon if we are seeing the same things by Tuesday I may be brave enough to call this.

Morning all - are we all ready for a 2 week rollercoaster ride? Have to say I'm a bit surprised this morning - I had expected at least one of the models to jump ship a bit and put the block in a poor place.... but perhaps the signals now are so strong that NWP cannot ignore the likely evolution.
The mother of all undercuts is now in place. Timing uncertain - in my book I suspect things are going to be moved forward gently, rather than back, but let's go with the best performing model and plump for this as the start of the peak period of cold and snow
Both UKMO and GFS show snow possibilities before this, but not of a severe nature to my eye - I'm past looking for fleeting snow showers and a 1 inch covering: what we can potentially gain from this upcoming spell is 15cm+ widely to all parts, and considerably more in lucky spots.
But we need to stay reflective. Charts at 216h rarely verify - even when all models seem to be pointing in the same direction there will be micro changes to the pattern. There are risks. The storm track could be forced so far south that all the snow ends up in France/Spain. This is a real risk. Less likely is that the undercut pushes further north as the block drifts towards the arctic... but for me that isnt going to happen. But it could. Atlantic barrels in - no chance. That risk was all but gone many days ago.
So.... first major frost on Wednesday morning, chances of snow flurries from Thursday onwards (it will certainly be cold enough in -4 uppers with a dry continental feed) and maybe some more sustained shower activity over the weekend... but all eyes looking for embedded troughs and possibly a major frontal system for the early part of the week after. By this stage the cold will have penetrated the ground a bit and provided an ideal surface for snow to fall (even given daytime frost melt under a warming sun....)
All good still. 1 in 10 to 1 in 20 year event on the horizon. I checked back through the archives for the "big" Februarys of recent decades: 2009, 1991, 1981 and 1978. The currently modelled synoptics surpass all of them... but just for fun I'll let you compare.
Feb 2nd 2009. Up to 50cm in places from this
Feb 7th 1991. 30cm widely from this.
Feb 22th 1981. 30cm from this, mainly for western parts
Feb 16th 1978. The famous "Great West Country Blizzard" showing that 30cm can fall widely (drifts of up to 24 feet!!) in marginal undercut scenarios
2018? Well - sod it - there's a wealth of heavy snow charts out there this morning... but this one from GFS would see all kinds of chaos...
Loving it.

The anomaly charts continue to support the overall pattern of northern blocking with lower heights south of this.
The 8-14 NOAA is as good for cold as I can remember for a good many years. How cold, how snowy then much too far ahead and these charts are not for that purpose. The synoptic models will give some idea but not this far out. T+72 or so for a GENERAL idea, T+12 for detail.
http://www.cpc.noaa.gov/products/predictions/814day/500mb.php
The ECMWF-GFS version also goes along with the NOAA advice
http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Hi Nick, that's the chart our experts over here have fairly high confidence now. We have been issued a extreme cold weather warning for next weekend with temps on the mountain Sunday morning down to -22c. The cold wave expected to align into the British Isles by this time next week. Snow showers should pack in over the North Sea. Our snow portal forecast has moderate accumulations over the Eastern Alps at the same time but the intense cold is the main concern in parts of Central Europe. Time now to watch for human input into the equation. Our forecast team expect a correction to the ECM model this evening with more progressive advection of the cold wave westward, also the warmer uppers further west on the UKMO. Just attached a picture of the resort of Rauris , a resort to the west of here as I will be staying there next weekend for a week. The massif to the top left is Gross Glockner, the highest mountain in Austria and the cold air will be a notable feature as it sinks and drains into the Rauris /WorthValley , so expecting sub -20c in that location, probabaly Mon morning.
C

Afternoon
What a great day...
Trying hard to add any more to the discussion - All I can really say is the archive charts being posted - even though they are the 'greats' like 2009 ~35cm here all have significantly WEAKER convection signals than currently being modelled -
The best chart of 2009 was this one-
heights dropping to 528 DAM
now look at the optimal flow from the ECM
516 DAM / -17 contour / gradient about 23 degrees across the North sea
I dont think many understand that this equates to the same as an early season lake effect snowsnow they get off the great lakes in canada when you can get 30-40cm a day in 5cm rates per hour-
Also the Snow ratio for the uk is always sloppy at about 1-6/7 so 1mm rain = 6/7cm of snow-
In this perfect scenario you would be looking at stella dendrites & 1:15 ratios - so huge depths.....
Just saying....
x

Oh - I cant resist another stock check. Apologies for sounding like a broken record, but it's a damned good one (think "Great Gig in the Sky" and "Number of the Beast" rolled into one....) Top Ten forecasting signals as follows:
1. Azores High. On very extended holiday as the storm track is fired south, and angular momentum at the equator remains positive for a while longer.
2. Vortex. Split and shredded. In reverse gear until March. No frictional downwelling support for any westerly momentum in the north atlantic.
3. Cold air. Spilling out all over the place as temperatures rise in the arctic stratosphere. Cold temps forecast throughout the northern hemisphere as a result, but Eurasian cold particularly noticeable due to total eradication of the Eurasian vortex, consequent swelling of the siberian high, and consequent strong signal for pattern retrogression.
4. Atlantic low pressure conveyor. Fighting a rearguard action as the Canadian vortex survives... but ongoing warming eating away at the foundations of that vortex and consequent trend for residual energy to slide under the growing Scandy block. Battleground scenarios for the West....
5. Ocean moderation of cold. Not significant... oceans in February are approaching coldest period.
6. Sun - growing - but in fact under a very cold airstream the warmth from the sun will promote a lot more shower activity. If 850s are lower than -8 then actually, perversely, we rather like a stronger sun.... (if you like snow that is...) Convective potential for the East.
7. MetO - in line. In fact in line for a while now... and rather than being an irritating voice of reason in the background, suggesting knife edge scenarios are not going to be significant or long lasting (with an even more irritating habit of being proved correct) instead is now sticking to a "very cold" scenario. BFF.
8, Genoa Low. Yep - its in place. Ensemble forecast sees low heights over the med for an extended period of time (see storm track point above) so potential for frontal systems to push SE to NW as per Feb 1991 perfectly in place. Snow for the South.
9. Pressure gradient. Yep - also in place. Scandy High set to get stronger... = slack winds a low risk
10. Cold in the north. Yeah - kinda repetitive this season I suspect... and maybe for once snow potential in the south may eclipse potential in the north.. but we all know its rarely dry in the north!! Snow will fall there too.
What have I missed? Doesnt really matter I suppose - all the above point in only one direction... There is a serious chance that Feb/March 2018 will end up in weather folklore.

Time to take stock...
Stratospheric split complete, reversal in operation - ECM 10 day forecast for the lower strat is significant
With clear signal for the expected nose of high pressure through the north atlantic, with virtually no westerly impact at all across Eurasia and a canadian vortex under stress from warming over Greenland. No downwelling support for an sustained atlantic assault, that's for sure.
At the tropics an interesting picture: tendency of equatorial angular momentum may have bottomed out
and with MT turning strongly positive
we have a current signature for GLAAM not falling too far or too fast. This may keep momentum positive over the longer term (lots going on here... is our Nina fading fast?? MJO renewal over the IO set to follow pretty swiftly??) and help maintain sufficiently low momentum profiles over the north atlantic to encourage the block further to the north.
In layman's terms what does this mean? Complex. I think Feb 2018 might be a much discussed month, dissected and reanalysed many times by students of SSW and GSDM alike - but the best guess at present remains the same as was the case over 10 days ago - height rises to the NE and a storm track pushed to the south underneath the block. This to retrogress over time, so heights transferring from Scandy to Greenland. This may not happen at the first attempt next week (though it might....), but likely on the second shortly after. Evidence? I think op runs will be chucked all over the place tonight - so let's instead look at 3 key ensemble charts.
Firstly CPC human adjusted chart that is usually a strong guide - 6-10 anomaly favourable
with EPS for day 10 also very good
and GEFS in line, though rather less strong in profile
Conclusion? CPC + ECM + GEFS (moderately) + strat profile (SSW, split and canadian vortex under stress) + pacific pattern (more neutral than supportive... but not overly negative) = a strong pathway of support pointing to cold inbound. Mid week as the jump off point, but early enough for snow lovers to get a fix before spring arrives, and longevity might be notable. Too early to be sure on that yet, but I dont think the trop pattern will recover swiftly from the present SSW.

Just a Gentle reminder that if you’re posting (sarcastic) disappointment at this morning’s output, there are a vast number of people reading that <trust> what posters in here are writing. That’s right! If you were to take every comment on face value then it’s all quite bewildering. We have been really really spoiled with mega charts the last five days and the 00z always seems to be the cause of the most woe every morning without fail there’s been an air of despair and for the 9000th time this week, it’s one run.
So whilst we have the willy waving, despair and ‘I told you so’ chat once again from the morning runs, please think about your post and it’s content.
Thanks!

I think some are worrying about small features that pop up in the models, which, physically won’t have much effect on the general well documented/agreed on momentum westwards of the deep cold as @Catacol has already highlighted. A small surface feature cannot alter the upper pattern and the jet, it’s normally the upper pattern and associated jet that dictates the movement of surface features.
The movement westwards of the deep cold is being driven partly/mostly by the remnants of the daughter vortex that formed from the split of the SPV by the SSW beginning of last week, which dropped into NE Europe / NW Russia and will now move west over Europe and is coupled with deep cold pool moving west in the troposphere.
This weakening strat vortex can be seen on the 2PVU loop below (in blue) on GFS tropopause (where trop meets strat) pressure charts, dropping south over NE Europe then moving west. This is in turn causing the jet stream to push SW across Europe – helping pull the cold air west and southwest. A small surface low or ‘shortwave’ as some like to call it won’t stop this momentum.
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i dont think anyone is ignoring the "elephant in the room", we're just hoping it will leave quietly without doing any damage. there has been a lot of volatility from all the models recently but they seem to be tapering towards a very cold spell for us. the ECM is not showing the best solution currently but whilst there is still some uncertainty, we have to look at the ensembles. the overwhelming conscensus is for an unprecedented cold snowy scenario for the UK. add to this, the consistency from the GFS operationals and @carinthian 's post above regarding professional opinion leaning against the ECM, we stand a very high chance of this 'ideal' scenario verifying. we are all, from past experience, very much aware that this is not guaranteed. however, though the ECM is one of the top models, it has been wrong before on many occasions and we can only hope this is one of them.
as for agendas? mine is wanting to help build my (almost six year old) daughter's first ever snowman.
she's seen a real life elephant but has never seen a real life snowman....